To charge an electric vehicle at a charging station, inductive charging systems are known. These involve coil systems being situated both on the underside of the electric vehicle and in the charging station on the ground. A magnetic alternating field that permeates this coil system is used to transmit power from the charging station to the electric vehicle by induction.
An inductive charging process can be performed after the electric vehicle is positioned on the charging station, without this requiring the vehicle driver to get out or a connection using a charging cable. To interchange position, identification and billing information, a communication link between the charging station and the electric vehicle has proved successful, which is maintained during the approach process and during the charging process when the electric vehicle is at a standstill.
In order to charge an electric vehicle by induction with low losses and little scattered radiation, it is necessary for the coil system of the charging station and the coil system of the electric vehicle to be positioned so as to overlap as exactly as possible. In addition, an explicit association needs to be made between the electric vehicle and the charging station. This explicit association or “associative connection” is required in order to ensure that the communication link is maintained only with that electric vehicle that is intended to be charged by induction on a predetermined charging station.
To ensure an explicit association between an electric vehicle and a charging station that is provided, there are already known methods. According to a proposal from the applicant that is disclosed in the document DE 102012012860 A1, there is provision for an associative connection to be provided between an electric vehicle and a charging station by virtue of an antenna on a vehicle being coupled to an antenna at the charging station, the arrangement of the vehicle antenna in relation to the charging station antenna being intended to ensure that only these two antennas can set up a shared connection. To this end, a directional characteristic of the charging station antenna is designed such that a signal radiated by the charging station antenna is receivable only in a prescribable area around a direct line of sight between the two antennas. In addition, there is provision for operation of the charging station antenna to be activated only when a prescribable area, particularly a charging position, is reached, in order to make it difficult to compromise the associative connection.
The issue of the associative connection being compromised that is addressed in the cited document has been found to be a problem in further field trials. As such, there is the risk of a transmitter in a radio area of the charging station behaving maliciously, posing as a remote station for an associative connection that is to be set up and, to this end, making its own transmission power exceed that of the inherently provided antenna of the charging station.